PXI question: four analog ouput cards to start-trigger simultaneously

Question

Hi all,
Here's the situation:
We have built a system that ouputs 24 analog signals using a PXIE-1073 chassis.  It has 5 slots:
Slot 1:          Internal
Slot 2:          Empty
Slot 3:          Empty
Slot 4 (Hybrid): PXI-6733
Slot 5 (Hybrid): PXI-6733
Slot 6 (Hybrid): PXI-6733
As you can see, it has three analog output cards, which occupy all three of the hybrid slots.  And we have two empty slots. 
Our LabVIEW code is designed to output analog signals on all three cards (at the same rate) using three DAQmx tasks which start-trigger simultaneously.  To do the triggering, we setup two of the tasks to start-trigger off of the first task (master-slaves style).  In this manner, we can get all outputs to start at the same time.  Its actually quite simple.
My question:  I want to add another output card.  But I am fairly I can only use hybrid slots for my application.  I remember working with NI and they told me I had to use the hybrid slots to be able to get the triggers routed automatically along the backplane.  Our code actually failed (error) when we used the non-hybrid slots (I forgot the error code).
Is there any way to add another PXI-6733 and have it trigger with the other cards?

Answer 1

I can't speak to the chassis, but I'd warn you that if you want your tasks sync'ed, you'd better share a sample clock too and not just a start trigger.  The onboard clocks will have a tolerance (often ~50 ppm, dunno for your 6733's)  and their sampling instants will drift apart from one another over time.  In fact, I rarely both with triggers at all for syncing tasks & boards.  I'll usually *only* share a sample clock, and then make sure I start all the slave tasks before the master whose sample clock is being shared.
Good luck on your real question though...
-Kevin P